A variety of fluid flow control valves and corresponding valve actuators are utilized for on/off control or throttling the flow of fluid, such as in a gas or oil pipeline system. The fluid flow control valves are typically sliding stem control valves or rotary action control valves and are operated by a valve actuator such as a pneumatic piston or diaphragm actuator responding to the output of a valve positioner for accurate throttling control of the valve.
For example, typically the fluid control valve is mounted in the pipeline system with the pneumatic actuator mounted on top of the valve and coupled to the valve fluid control element. If utilized, a positioner is mounted to the side of or above the actuator. Thus, the overall valve, actuator and positioner assembly can be a fairly large and heavy combination of elements extending for some distance above the valve and projecting therefore above the pipeline and possibly greatly beyond the valve itself.
It is desired to provide an actuator for fluid control valves of reduced height and weight and with fewer component parts so as to reduce manufacturing costs and hopefully increase operational reliability.